Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

19. Reactions of Aromatics: EAS and Beyond

EAS:Friedel-Crafts Alkylation Mechanism

Organic Chemistry

19. Reactions of Aromatics: EAS and Beyond

EAS:Friedel-Crafts Alkylation Mechanism

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5:12 minutes

Problem 50c

Textbook Question

Predict the major products formed when benzene reacts (just once) with the following reagents.
c. isobutyl alcohol + BF₃

Verified step by step guidance

Step 1: Recognize the type of reaction. This reaction involves benzene and isobutyl alcohol in the presence of BF₃ (boron trifluoride). BF₃ is a Lewis acid, which can facilitate the formation of a carbocation from isobutyl alcohol. This suggests that the reaction will proceed via an electrophilic aromatic substitution (EAS) mechanism.

Step 2: Generate the electrophile. BF₃ interacts with isobutyl alcohol to form a carbocation. The hydroxyl group (-OH) of isobutyl alcohol is protonated and leaves as water, resulting in the formation of a tertiary carbocation: (CH₃)₂CH⁺CH₂⁺.

Step 3: Identify the site of attack. Benzene, being electron-rich, will act as a nucleophile and attack the carbocation. This forms a sigma complex (also called an arenium ion), where the benzene ring temporarily loses aromaticity.

Step 4: Restore aromaticity. A proton (H⁺) is removed from the sigma complex by a base (often the BF₄⁻ counterion or another molecule in the reaction mixture), restoring the aromaticity of the benzene ring. The final product is an alkylbenzene, where the isobutyl group is attached to the benzene ring.

Step 5: Predict the major product. Since the isobutyl carbocation is relatively stable due to hyperconjugation and inductive effects, the major product will be isobutylbenzene, where the isobutyl group is directly bonded to the benzene ring.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Electrophilic Aromatic Substitution

Electrophilic aromatic substitution (EAS) is a fundamental reaction mechanism in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. In this process, the aromatic system donates electrons to the electrophile, forming a sigma complex, which then loses a proton to restore aromaticity. Understanding EAS is crucial for predicting the products of reactions involving benzene and electrophiles.

Lewis Acids and Bases

Lewis acids are species that can accept an electron pair, while Lewis bases are those that can donate an electron pair. In the context of the reaction with isobutyl alcohol and BF3, BF3 acts as a Lewis acid, facilitating the formation of a more reactive electrophile. Recognizing the roles of Lewis acids and bases is essential for understanding how they influence reaction pathways and product formation.

Friedel-Crafts Alkylation

Friedel-Crafts alkylation is a specific type of electrophilic aromatic substitution where an alkyl group is introduced to an aromatic ring using a Lewis acid catalyst. In this case, the isobutyl group from isobutyl alcohol can be transferred to the benzene ring in the presence of BF3. This concept is vital for predicting the structure of the major product formed in the reaction.

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Related Practice

Textbook Question

Propose products (if any) and mechanisms for the following AlCl₃-catalyzed reactions:

a. chlorocyclohexane with benzene

Textbook Question

Predict the products.

Textbook Question

Propose products (if any) and mechanisms for the following AlCl₃-catalyzed reactions:

b. methyl chloride with anisole

Textbook Question

Predict the major products formed when benzene reacts (just once) with the following reagents.

a. tert-butyl bromide, AlCl₃

b. 1-chlorobutane, AlCl₃

Textbook Question

Electrophilic aromatic substitution usually occurs at the 1-position of naphthalene, also called the a position. Predict the major products of the reactions of naphthalene with the following reagents.

(d) isobutylene and HF

Textbook Question

Electrophilic aromatic substitution usually occurs at the 1-position of naphthalene, also called the 1-position. Predict the major products of the reactions of naphthalene with the following reagents.

(e) cyclohexanol and BF₃

Textbook Question

For each reaction, show the generation of the electrophile and predict the products.

c. tert-butylbenzene + 2-methylpropene + HF

Textbook Question

For each reaction, show the generation of the electrophile and predict the products.

d. propan-2-ol + toluene + BF₃

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Predict the major products formed when benzene reacts (just once) with the following reagents.c. isobutyl alcohol + BF3

Key Concepts

Electrophilic Aromatic Substitution

Lewis Acids and Bases

Friedel-Crafts Alkylation

Watch next

Predict the major products formed when benzene reacts (just once) with the following reagents.
c. isobutyl alcohol + BF₃